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NIST denies it weakened its encryption standard to please the NSA

Bruce Schneier tells agency its credibility is shot

The US National Institute of Standards and Technology (NIST) has vehemently denied accusations that it deliberately weakened encryption standards to help the NSA's monitoring activities.

"We want to assure the IT cybersecurity community that the transparent, public process used to rigorously vet our standards is still in place," said NIST in a statement.

"NIST would not deliberately weaken a cryptographic standard. We will continue in our mission to work with the cryptographic community to create the strongest possible encryption standards for the U.S. government and industry at large."

According to a memo released by NSA whistleblower Edward Snowden, the intelligence agency's budget included efforts to "influence policies, standards and specifications for commercial public key technologies". In particular, NIST Special Publication 800-90 was referenced, a 2006 encryption standard adopted by NIST which uses four deterministic random bit generators.

One of these generators, Dual_EC_DRBG, is based on finding the discrete logarithms of elliptic curves and attracted attention almost immediately, not least because it was considerably slower than the other three methods and was specifically championed by the NSA.

A year after its publication, two Microsoft researchers – Dan Shumow and Niels Ferguson – gave a presentation at the CRYPTO 2007 conference which suggested that Dual_EC_DRBG was crackable. They were careful not to accuse the NSA of deliberately inserting a backdoor into the system, but noted that it was potentially unsafe.

In Tuesday's statement, NIST said that working with the NSA was standard operating procedure; indeed it was required by law to consult with the NSA on security matters. To reassure users, NIST has reopened the standard to public comment so that it can be checked, but cryptography expert Bruce Schneier, who has examined some of Snowden's material on the matter, warned that this won’t be good enough.

"NIST took a big credibility hit unfortunately," he said in a podcast. "There are good people there doing good work but we don't know which of their standards are tainted, we don't know how much collaboration there is with the NSA.

"And unfortunately because trust is lost when they get up and say the NSA doesn't affect our standards we don't believe them. We need a way to get back trust."

Schneier likened the situation to betraying a spouse, saying that in that kind of situation the only way to get trust back is by full disclosure. "You can't say 'here's most of the things I did and you may find out some more in a few months' – those sort of strategies never work." ®